US20140161590A1

US20140161590A1 - Cover device, integrally bladed main rotor body, method and turbomachine

Info

Publication number: US20140161590A1
Application number: US14/114,853
Authority: US
Inventors: Frank Stiehler; Manuel Hein
Original assignee: MTU Aero Engines AG
Current assignee: MTU Aero Engines AG
Priority date: 2011-05-02
Filing date: 2012-04-25
Publication date: 2014-06-12
Also published as: WO2012149925A3; EP2705218A2; WO2012149925A2; DE102011100221B4; DE102011100221A1

Abstract

A covering device for an integrally bladed rotor base body of a turbomachine for preventing or reducing a cooling air stream that flows from a high-pressure side to a low-pressure side through channels that are formed between adjacent rotor blades, a plurality of cover elements being provided that are individually insertable into the channels and have at least one peripheral sealing surface. Also an integrally bladed rotor base body having a covering device of this kind, a method for producing such an integrally bladed rotor base body, as well as a turbomachine having such an integrally bladed rotor base body.

Description

The present invention relates to a covering device for an integrally bladed rotor base body according to the definition of the species set forth in claim 1, an integrally bladed rotor base body having a covering device of this kind, a method for assembling an integrally bladed rotor base body of this kind, as well as to a turbomachine.
Integrally bladed rotor base bodies of a rotor for turbomachines, such as aircraft engines, for example, having a plurality of rotor blades that are joined in a substance-to-substance bond to a disk-, respectively ring-shaped base body, and rotor blades forming a blade row have a channel-type passage which, for reasons of production engineering, is adjacently disposed at regular intervals between blade roots, respectively blade shafts, and through which cooling air can flow axially from the high-pressure side to the low-pressure side. To prevent, respectively at least reduce a cooling air stream flowing through the channels, the German Patent Application DE 10 2009 007 468 A1 provides for using a covering device to seal the channels on the outlet side, i.e., the low-pressure side. The covering device includes a sheet metal-type ring which grips around the base body and is configured between a radially inner hook-shaped holder and a radially outer hook-shaped holder. The ring does, in fact, provide a reliable sealing of the channels, respectively a reliable reduction of the channel cross sections, but it is relatively heavy. Moreover, manufacturing the holders is a costly and technically complex. An alternative covering device, which is likewise described in the German Patent Application DE 10 2009 007 468 A1, has a plurality of tubular cover elements which are configured in and extend beyond the channels and whose lumen can be reduced in size or sealed. The cover elements are secured at the ends by a tubular collar and thus by form-locking engagement. The inherent disadvantages of this alternative covering device are a high outlay for assembly and disassembly, and likewise the relatively high weight thereof.
It is, therefore, an object of the present invention to provide a covering device for an integrally bladed rotor base body of a turbomachine that will overcome the aforementioned disadvantages and, in addition, be able to be readily assembled and disassembled. It is also an object of the present invention to provide an integrally bladed rotor base body for a turbomachine having an optimized covering device, a method for assembling an integrally bladed rotor base body of this type, as well as a turbomachine.
This objective is achieved by a covering device having the features of claim 1, by an integrally bladed rotor base body having the features of claim 8, by a method having the features as recited in claim 12, as well as by a turbomachine having the features of claim 15.
A covering device according to the present invention for an integrally bladed rotor base body of a turbomachine for adjusting a cooling air stream flowing from a high-pressure side to a low-pressure side through channels that are formed between adjacent rotor blades, has a plurality of cover elements that may be individually inserted in the channels and that feature at least one peripheral sealing surface.
It is advantageous that the cover elements are inserted into the channels, so that there is no need for configuring the previously mentioned holders. It is also advantageous that the at least one peripheral sealing surface makes it possible for the cover elements to be configured in the channels in quasi any desired manner, thereby simplifying the assembly and disassembly thereof. In addition, the opening cross sections of the channels may be individually adjusted. For example, it is possible to control the closing of individual channels and the reduced opening of other channels.
It turns out that adequate sealing is already achieved when the sealing surface in question has a smaller axial extent than the respective channel, further simplifying the assembly and disassembly. In addition, the weight of the covering device, respectively of the individual cover elements is reduced by the short axial extent.
The cover elements preferably have a cuplike, respectively hatlike profile having an outer body section, such as a collar. The body sections make it possible to accurately position the cover elements in the channels during assembly. Following assembly, the body sections act as axial securing elements for the centrifugally loaded cover elements. In another exemplary embodiment, the cover elements are centrifugally activatable. It is hereby merely necessary to position the cover elements movably, respectively loosely in the channels, thereby further simplifying both the assembly, as well as the disassembly.
In accordance with one modular design, the cover elements may have a plurality of assemblable and disassemblable individual parts. The modular design makes it possible to combine various cover disks and connecting arms with one another, so that a large number of different cover elements may be produced using a small number of cover disks and connecting arms. Moreover, it is a feature of the modular design that, should one of the components be defective, it is merely necessary to replace it with a new part.
In one preferred exemplary embodiment, the cover elements have two cover disks and a connecting arm releasably interconnecting the same. The two cover disks make possible a double adjustment of the channel cross sections, for example, to allow a reduced cooling air stream to enter into the channels via the front cover disk, in order then to direct the same to a blade-internal cooling air system. The channels are then sealable on the outlet side by the rear cover disk, preventing an axial cooling air stream from flowing through the channels, and ensuring that the reduced cooling air stream is used exclusively for internal blade cooling. On the other hand, the cover disks may stabilize one another, particularly when combined with the centrifugally activatable cover elements, preventing them from being able to tilt away or jam in the channels and always ensuring an optimal sealing.
To allow a reduced cooling air stream to enter into the channels and/or emerge therefrom, the cover elements may feature overflow openings. The overflow openings may be formed as bores, for example, or configured as axial circumferential grooves in the particular sealing surface.
An integrally bladed rotor base body according to the present invention for a turbomachine having a plurality of rotor blades has a covering device having a plurality of cover elements for adjusting a cooling air stream flowing from a high-pressure side to a low-pressure side through channels that are formed between adjacent rotor blades, at least one cover element having at least one peripheral sealing surface being inserted in each channel.
An integrally bladed rotor base body of this kind is distinguished by smooth running properties since the cover elements are only configured in the channels, and no, respectively only very small additional masses are introduced into the rotor blades, so that the cover elements do not cause any, respectively cause virtually no repercussions on the vibration mechanics of the rotor blades. Moreover, an effective mutual delimitation and guidance of the cooling air streams and of the hot gas streams are also achieved.
In one exemplary embodiment, the sealing surfaces are configured in the channels in a way that allows them to be positioned by the at least one sealing surface thereof on the inlet or outlet side and, thus, at the ends in the channels, thereby simplifying the assembly and disassembly, in particular.
The cover elements may be fixed in the channels in each case under force- and form-locking engagement, and, in this context, rest on the front side by the respective, radially outer body section thereof against the rotor blades, thereby securely accommodating them in the channels, and accurately positioning them by the body sections. A reliable positional fixation and optimal sealing are thus achieved by the force- and form-locking engagement. In addition, component and assembly tolerances may be compensated, in particular, by the force-locking engagement.
In another exemplary embodiment, the cover elements are configured axially displaceably in the channels and axially secured by a securing element, at least on one side. In response to rotation of the rotor base body, the centrifugal force moves the cover elements radially outwardly in the channels, causing them to be pressed by the sealing surfaces thereof against the wall sections of the channels. Depending on the orientation and profile of the channels, the securing elements prevent the cover elements from falling out in stillstand or from being pushed out during operation. One individual securing element may be provided for each cover element or, however, a securing element may be provided for a plurality of cover elements.
One method according to the present invention for manufacturing a preferred integrally bladed rotor base body provides that the cover elements be configured in the area of the at least one sealing surface thereof to have a cross section that corresponds approximately to a cross section of a channel section that receives the same. The cover elements are then positioned in the channel sections. By adapting the cross sections of the cover elements to the respective channel cross sections, the assembly is facilitated, and it is also thereby ensured that the cover elements are able to be positioned in the nominal position thereof.
One exemplary embodiment provides for using a forming process to radially widen the cover elements to attain positional fixation, a radially outer body section being advantageously quasi formed as a positioning aid and, subsequently to the deformation process, as a securing element, thereby allowing the cover elements to be held by force- and form-locking engagement in the channels. The cover elements are preferably preformed to include the collar, keeping the degree of deformation to a minimum and preventing any excessive deformation forces from damaging the cover elements. It is also possible, however, that the collars already be provided with the final contour thereof, eliminating the need for forming of the same. In particular, the cover elements are pressed in and conform, for example, to a radially outwardly and conically expanding inner contour of the channels. They are thus secured in both axial directions. Alternatively, however, the cover elements may also be accommodated in the channels in a manner that allows for tolerance deviations. In one exemplary embodiment where the cover elements are composed of a plurality of individual parts, they are at least separately assembled following introduction thereof into the channel, so that, by selecting appropriate individual parts, it is possible to compensate for component tolerances of the channels.
A turbomachine according to the present invention has at least one integrally bladed rotor base body in accordance with the present invention and features a very effective delimitation of a hot gas stream from a cooling air stream, smooth running properties, and very easy maintainability with regard to the rotor blade-side axial covering device.
Other advantageous exemplary embodiments of the present invention constitute the subject matter of other dependent claims.

Preferred exemplary embodiments of the present invention are described in greater detail in the following with reference to schematic representations. In the drawing,

FIG. 1 shows a front view of a portion of an integrally bladed rotor base body in the area of two adjacent rotor blades, including a first exemplary embodiment of a covering device in accordance with the present invention;

FIG. 2 shows a rear view of a cover element shown in FIG. 1;

FIG. 3 shows a cross-sectional view taken along the radial plane of the integrally bladed rotor base body from FIG. 1;

FIG. 4 shows a front view of a portion of an integrally bladed rotor base body in the area of a rotor blade, including a second exemplary embodiment of the covering device according to the present invention;

FIG. 5 shows a side view of the integrally bladed rotor base body from FIGS. 4; and

FIG. 6 shows a rear view of the integrally bladed rotor base body from FIG. 4.

FIGS. 1 and 2 each show a portion of an integrally bladed rotor base body 1 for a turbomachine, such as an aircraft engine, for example, in a perspective front view (FIG. 1) and in a perspective rear view (FIG. 2). Rotor base body 1 has a plurality of adjacent rotor blades 2 that form a blade row and are joined to a turbine-side ring- or disk-shaped base body 4.
The rotor blades each have a blade root 6, a blade neck 8, a blade leaf 10, and a platform 12, which is configured between blade neck 8 and blade root 10 and (viewed in the flow direction of a hot gas stream) includes a front, high pressure-side projection 14 and a rear, low pressure-side projection 16.
Blade root 6 is either configured as an integral part of rotor blade 2 or as a separately formed component that is joined to rotor blade 2 in a subsequent process. It is joined by the radially inner peripheral surface thereof to a pedestal (not shown) of base body 4 by a substance-to-substance bond, for example, a friction welding process, and has two concavely formed side walls 18, 20 shown in FIG. 2, which each merge transitionally into and flush with a base body-side peripheral wall 22.
In comparison to blade root 6, blade neck 8 has a widened shape. It has two laterally, mutually opposed recesses 24 that are rimmed by a lateral surface 26, 28, respectively. Lateral surfaces 26, 28 extend in each case over projections 14, 16 and are each provided in a platform-distal and a channel-proximate region with an axially extending, inwardly stepped portion 30. In addition, as in the case of a second exemplary embodiment in accordance with the present invention shown in FIG. 4, in the area of rear projections 16, lateral surfaces 26, 28 may each be provided with a peripherally extending, inwardly stepped portion 32 in order to produce a fluid communication between a cavity 34 (see FIG. 3) formed by each of opposing recesses 24 and a low-pressure side of rotor blades 2.
Blade 10 extends approximately from the middle of platform 12 and is of a conventional type, so that there is no need for a detailed explanation here. In principle, it may be provided with an internal cooling system (see FIG. 5).
Platform 12 is formed by blade neck 8 and, together with platforms 12 of adjacent rotor blades 2, forms a radially outer, hot gas stream-side annular space 38 denoted in FIG. 2 and a radially inner cooling air stream-side cooling space 40.
As shown in the greatly simplified radial plane sectional view according to FIG. 3 in the direction of flow, adjacent rotor blades 2 each have a lateral contact region 36. Adjacent rotor blades 2, together with opposing lateral surfaces 26, 28 thereof, contact one another and thus form annular space 38 and cooling space 40. Mutually opposing lateral walls 18, 20 of rotor blades 2 each peripherally define a channel 42 that is in radial fluid communication via a gap 44 formed by inwardly stepped portions 30 with hollow space 34 formed by mutually opposing recesses 24. As is discernible in FIG. 1, channels 42 are obliquely positioned relative to the axis of rotation, and each have a high pressure-side, radially inner inlet and a low pressure-side radially outer outlet. The mutually opposing, peripherally extending, inwardly stepped portions 32 (not discernible in the sectional view) of rotor blades 2 each form a low pressure-side outlet orifice that communicates axially with cooling space 40.
To adjust a cooling air stream flowing through channels 42 in the axial direction from the high-pressure side to the low-pressure side of rotor blades 2, as well as in the radial direction between the hot gas stream and the cooling air stream through contact regions 36, and, in the process, also between channels 42 and hollow spaces 34 through gaps 44, i.e., to prevent or reduce the same, a first covering device 46 according to the present invention having a plurality of cup-shaped cover elements 48 is provided, as shown in FIGS. 1 and 2.
As denoted in FIG. 2, cover elements 48 each have a cup-shaped profile having a conical wall 50, a bottom 52, and a top-end, radially outer collar 54. They are made of a readily cold-deformable, heat-resistant steel, such as a nickel-based alloy and are preferably configured on the inlet side in channels 42.
Conical wall 50 has cross sections that correspond to cross sections of an inlet-side surface section 56 of channels 42 that accommodate the same and form an outer peripheral-side sealing surface 58. In the illustrated assembled state, wall 50 rests by sealing surface 58 thereof sealingly against surface section 56. The conicity of wall 50 corresponds to that of respective channel 42, so that, in the exemplary embodiment shown in FIGS. 1 and 2, cover elements 48 are radially widened starting from collar 54 thereof in the direction of bottom 52 thereof.
Bottom 52 has a closed design. However, it may also have an overflow opening 60 through which cooling air may flow into an internal blade-side cooling system through an inlet bore 62 (see FIG. 5) extending through side walls 26, 28 (see FIG. 5).
During assembly, collar 54 forms a positioning aid in each case for accurately positioning respective cover element 48 in channels 42. In the assembled state, it engages on end face portion 64 of blade roots 6 surrounding channels 42 in a frame-like manner and then acts as an integral, one-sided axial securing element. Thus, in combination with conical wall 50, both a movement of respective cover element 48 in the flow direction, as well as in the opposite direction are prevented.
For the assembly, cover elements 48 are pushed as shown by the arrow in FIG. 2, from the low-pressure side to the high-pressure side and thus rearwardly into channels 42, until they project by the top portions thereof out of channels 42 on the inlet side. A tool is then applied to cover elements 48 in the direction of flow, respectively from the front, and collar 54 thereof is produced by edge forming under compression. At the same time, sealing surfaces 58 are pressed against surface portions 56 of channels 42, so that cover elements 48 are accommodated in channels 42 without clearance and under compression. Due to the conicity of channels 42 and subsequently edge-formed collar 54, cover elements 48 are secured against axial displacements by force- and form-locking.
To keep the deformation forces acting on cover element 48 and thus the degree of deformation to a minimum, collars 45 may also be slightly edge-formed already prior to insertion of cover elements 48. Alternatively, collars 54 may be manufactured to the final dimensions thereof already prior to insertion of cover elements 48 into channels 42, eliminating the need for forming collars 54. When collars 54 are slightly edge-formed or already manufactured to the final dimensions, covering elements 48 are inserted from the front into channels 42 and, for purposes of press-fitting, brought into engagement by collars 54 thereof with a front disk (not denoted).
Another method variant provides for configuring cover elements 48 in channels 42 in a process that allows for tolerance deviations. Cover elements 48 are plastically deformed in such a way that form-locking engagement secures them against falling out of channels 42. However, they are pressed radially outwardly by centrifugal force and thereby seal channels 42.
To provide axial securing, a modification also makes it possible for cover elements 48 to be configured on the rear side and thus on the outlet side in channels 42. In the same way, cover elements 48 may be configured on the inlet side and outlet side and thus, in each case, in pairs in channels 42.
FIGS. 4, 5 and 6 each show a second exemplary embodiment of a covering device 46 according to the present invention for adjusting a respective cooling air stream, in each case flowing through an axial blade root-side channel 42 and, thus, indirectly through a gap 44, in each case in a contact region 36 of adjacent rotor blades 2 of an integrally bladed rotor base body 1 (compare FIG. 3).
In accordance with FIG. 4, covering device 46 has a plurality of centrifugally activatable covering elements 48 configured in channels 42, each having a dumbbell shape and including two end- side cover disks 66, 68, that are releasably interconnected via a connecting arm 70.
Cover disks 66, 68 are plate-type members, preferably cast bodies, having a cross section that corresponds to the respective channel cross section. Due to the conicity of channels 52, which is provided here exemplarily, outlet-side cover disks 68 have a larger cross-sectional area than do inlet-side cover disks 66. As specified in FIG. 5, they each have a peripheral sealing surface 58, 72 for engaging on corresponding inlet-side and outlet- side surface sections 56, 74 of channels 42. To allow cooling air to be introduced into an inlet bore 62 of a blade-side cooling air system, cover disks 66, 68 may feature corresponding overflow openings (not shown) in the form of axial peripheral grooves or bores (compare overflow opening 60 in FIG. 2).
Connecting arm 70 has a T-shaped cross section having a plurality of weight-reducing openings 76 denoted in FIG. 5. It is anchored by an end portion thereof to one of cover disks 66. It is passed by unattached end portion 78 thereof through an opening of unattached cover disk 68 and releasably connected thereto by a locking element 80, such as a shaped sheet-metal piece or a wire. In the exemplary embodiment shown in FIGS. 4, 5 and 6, connecting arm 70 is fixed to inlet-side cover disks 66.
During operation, cover elements 48 are pressed outwardly by the centrifugal force into channels 42. An axial limit stop (not shown) is provided on the blade side to prevent cover elements 48 from being forced out of channels 42 in the case that channels 42 have a constant cross section or extend conically toward one side. Depending on the conicity form, an axial limit stop is needed to protect against any falling out from channels 42 at standstill or during operation. If, for example, as shown in FIGS. 4, 5 and 6, channels 42 have an outlet that is disposed radially outwardly relative to the inlet thereof, and are conically widened in the direction of the outlet, a limit stop is needed to prevent cover elements 48 from being ejected from channels 42 during operation in response to the centrifugal force. If, on the other hand, channels 42 have an outlet that is disposed radially outwardly relative to the inlet thereof and are conically tapered in the direction of the outlet, a limit stop is needed to prevent any falling out at standstill. If channels 42 have a constant cross section over the axial length thereof, a limit stop is needed both on the inlet side, as well as on the outlet side.
Cover elements 48 are assembled in channels 42; cover disks 66 being first positioned in channels 42 via attached connecting arm 70, and unattached cover disks 68 then being fitted onto unattached end portion of respective connecting arm 70. Unattached cover disks 68 are then secured to end portions 78 by positive-engagement locking elements 80.
A covering device is described for an integrally bladed rotor base body of a turbomachine for preventing or reducing a cooling air stream that flows from a high-pressure side to a low-pressure side through channels that are formed between adjacent rotor blades; a plurality of cover elements being provided, which are individually insertable into the channels and at least have a peripheral sealing surface. Also described are an integrally bladed rotor base body having a covering device of this kind, a method for manufacturing an integrally bladed rotor base body of this type, as well as a turbomachine having an integrally bladed rotor base body of this type.

Claims

1-15. (canceled)

16. A covering device for an integrally bladed rotor base body of a turbomachine for adjusting a cooling air stream flowing from a high-pressure side to a low-pressure side through channels formed between adjacent rotor blades, the covering device comprising:

a plurality of cover elements, the cover elements being individually insertable into the channels and having at least one peripheral sealing surface, wherein the cover elements are centrifugally activatable.

17. The covering device as recited in claim 16 wherein at least one of the cover elements has at least one sealing surface having an axially shorter extent than the channel accommodating the at least one cover element.

18. The covering device as recited in claim 16 wherein the cover elements each having disassemblable individual parts.

19. The covering device as recited in claim 18 wherein the cover elements each having two cover disks and a connecting arm releasably interconnecting the cover disks.

20. The covering device as recited in claim 16 wherein the cover elements each have overflow openings.

21. An integrally bladed rotor base body for a turbomachine comprising:

a plurality of rotor blades; and

a covering device as recited in claim 16 having the plurality of cover elements for adjusting the cooling air stream, at least one of cover elements having at least one peripheral sealing surface being inserted in the channel.

22. The integrally bladed rotor base body as recited in claim 21 wherein the sealing surface is positioned at an end in the channel.

23. An integrally bladed rotor base body as recited in claim 21 wherein the cover elements are each configured axially displaceably in the channels and are axially secured by a securing element at least on one side.

24. A method for producing an integrally bladed rotor base member as recited in claim 21, comprising the steps of:

forming the cover elements to have a cross section in the area of the at least one sealing surface corresponding approximately to a cross section of a channel section that receives the respective cover element; and

positioning the cover elements in the channel sections.

25. A turbomachine comprising an integrally bladed rotor base body as recited in claim 21.